BEHAVE	Designation of a fire behaviour prediction system, based on a semi-empirical fire propagation model developed by R. Rothermel and co-workers in Missoula. Also known as Rothermel’s model.
Ignition	The initiation of the exothermic phase of the overall pyrolisis / combustion reaction; it may result in glowing or flaming combustion.
Backfire	Fire set intentionally to fuels inside the control line to contain a rapidly spreading fire in an indirect attack. Same as counterfire.
Fire Break	A natural or constructed barrier utilised to stop or slow down a fire that may occur, or to provide a control line from which to work.
Basic Fuel Model	The most common or dominant fuel model in a given area, on which fire danger and fire behaviour calculations are made, to assess the means to face a given situation.
Biomass	The dry weight of all organic matter in a given ecosystem. It also refers to plant material that can be burned as fuel.
Global fire propagation models	Fire behaviour models which describe or predict the overall evolution of the fire front.
Wildland-Urban Interface	That line, area or zone where structures and other human developments meet, or intermingle with undeveloped wildland or vegetative fuels.
Fire Line Intensity (I)	Amount of heat liberated per unit of time by unit width of the fire front: I=Q.R.W. (Q: Heat content, R: rate of spread, W: fuel per unit area that is consumed by the fire).
Fire Risk	The probability of fire initiation due to the presence and activity of a causative agent.
Surface Fuel	The loose surface litter on the forest floor, normally consisting of fallen leaves or needles, twigs, bark, cones and small branches that have not decayed sufficiently to lose their identity. Also grasses, shrub and tree reproduction less than 4 feet (1,2 meters) in height, heavier branch wood, down logs, stumps, seedlings and forbs interspersed with, or partially replacing the litter.
Surface Fire	Fire that burns only surface litter, other loose debris of the forest floor, and small vegetation.
Flammability	The relative ease with which a substance ignites and sustains combustion.
Living Fuel	Naturally occurring fuels in which the moisture content is physiologically controlled.
Combustion	Uniting of a fuel and an oxidant in a chemical reaction which releases significant heat and is accompanied by the emission of light.
Ladder fuels	Fuels that provide vertical continuity between the surface fuels and crown fuels in a forest stand, thus contributing to the ease of torching and crowning.
Fine Fuels	Fuels composed by particles considered thermally thin. Normally assigned arbitrarily with a minimum dimension not exceeding 5 mm.
Dead Fuel	Naturally occurring fuels without biological activity and so in which the moisture content is controlled almost entirely by solar radiation, atmospheric moisture (relative humidity and precipitation) and temperature.
Fuelbed Porosity	Fraction of the total volume of a fuel layer that is occupied by air. Also called, or expressed, by packing ratio.
Greenbelt	An extensive area of largely undeveloped or sparsely occupied land, associated with a community set aside to contain development, preserve the character of the countryside and community, and provide open space.
Management-ignited prescribed fire	The planned application of fire to natural fuels, including logging debris, grasslands and/or understory vegetation, such as palmettos, with the intent to confine the fire to a predetermined area.
Fire	A self-sustaining chemical reaction that can release energy in the form of light and heat.
Fuel Continuity	Horizontal distribution of fuel.
Speed of attack	Time elapsed between the beginning of a fire and the arrival of the first suppression force.
Local Models (surface fires)	Fire behaviour models aimed at predicting the quasi-steady evolution of a small section of the fire front, under statistically homogenous and constant local fuelbed and ambient conditions.
Fuel Type	A group of fuels possessing common characteristics such as herbaceous, low shrubs, medium shrubs, deciduous trees, coniferous.
Fuel Moisture	Mass of water content per unit mass of dry fuel. Moisture content is determined by oven drying at 85oC a sample of fuel during 24h.
Slash	Debris left on the ground after logging, pruning, thinning, or brush cutting, or after the passage of a wind storm or a fire. Includes logs chunks, bark, branches, stumps and broken understory or brush.
Moisture time lag	The amount of time necessary for particle of fuel to reduce approximately 63% of the difference between the initial moisture content and its EMC when exposed to permanent air temperature and humidity conditions.

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